PEAESE. — THE REACTIONS OF AMPHIBIANS TO LIGHT. 187 



did not show twenty successive reactions on the day considered. 

 Under (a) sixty such sets of daily records are included, and under (b), 

 forty-three sets. The toads reacted more slowly after having been 

 kept in the dark than after they had been exposed to light. The 

 difference is not great and cannot be considered very significant in 

 showing optic influence. The results may, however, be interpreted as 

 indicating that prolonged exposure to light renders the toad more 

 photokinetic. 



G. The Reactions of Amphibians to Lights of Different 



Colors. 



In testing the reactions of animals to lights of different wave lengths 

 the apparatus shown in Figure 6 was used. Animals were placed in 

 the position shown in the figure, and after each reaction they were 

 rotated clockwise through 180°. The right and left sides were thus 

 brought alternately toward the light, which had an intensity of 612 

 candle-meters (for white light) at the point where the animals were 

 placed. The different colors were obtained by passing the white light 

 of a Nernst lamp through colored screens. These screens were 

 solutions of various substances held in rectangular glass jars which 

 could be easily interchanged. 3 The colors used were red, yellow, green, 

 and blue, and, though they were not perfectly monochromatic, they 

 did not overlap significantly in the spectrum. 



3 The substances used in making the solutions and the ranges of the 

 colors obtained from them, as determined by an Engelmann spectroscope, 

 were as follows : 



